The present invention relates generally to a pressure vessel having removable lid, of the type that are used for storing objects under pressure and more particularly it relates to a pressure vessel suitable for storing a large number of gas pressurized balls, such as tennis balls, under an external pressure to maintain the optimum playing characteristics of the individual balls.
Many types of pressurized balls, and in particular, tennis balls, suffer a loss of liveliness over time. More specifically, tennis balls are packaged under pressure at the factory in hermetically sealed containers. It is necessary to break the seal and release the pressure from the container before play can commence with the tennis balls. This results in the tennis balls having a greater pressure inside than outside which pressure gradually equalizes with ambient air over time. Depending upon the degree of pressure loss, the performance characteristics of the ball deteriorate to the point that the ball is unfit for play. What is desired is a pressurized environment which reduces or eliminates the tendency of the tennis balls to lose pressure over time, at least while subject to the pressurized environment.
Many attempts have been made to provide a resealable container which is capable of maintaining tennis balls under pressure. Some examples of such devices are disclosed in the following U.S. Pat. Nos. 3,415,357; 3,853,222; 3,888,347; 3,889,807; 3,897,874; 4,019,629; 4,020,948; 4,101,029; 4,124,117 and 4,161,247.
These devices rely on both gas pressurization or mechanical pressing of bellows or the like. Some have been proposed for use in associatron with a limited number of balls, typically three. However, what is desired is a pressure vessel which can accommodate more than three balls.
An example of a larger multi-ball storage device is found in U.S. Pat. No. 4,101,029. However, this patent discloses a pressure vessel with a center post and a sealing ring which combine to make the use of the device very awkward. For example, to remove the lid requires first that the pressure be released, then the cover assembly must be depressed against a spring on the center post, then the seal must be pulled away from the rim of the lid, then the center post may be raised again, then the handle at the top of the center post must be unscrewed, then the lid may be removed. The only way balls can be removed from the container is to remove the lid. In the unassembled position, there are three separate components apart from the pressure vessel itself, namely the seal, the lid, and the handle. Any of these components may be lost or misplaced which is undesirable. Further, the number of steps involved in removing and repositioning the lid make this device awkward and difficult to use.